RM is a fantastic tool for data mining research and application. Thanks for your good work. Here I have a problem when I use the 04_XValidation_Nominal.xml sample. Theoretically, when the "sampling_type" parameter is set to be "stratified sampling" and "local_random_seed" is set to be -1, the results should be a little different in different iteration of running, since each time the training sample and test sample are different in each fold validation. In my test, the result has no change. I tried several other example source, it still has no change. Could anybody tell me what's the problem. Thanks again.

setting the "local_random_seed" to -1 means: use the global random seed. The global random seed is initialized everytime you start the process. This is necessary because otherwise you were not able to recompute your results. However, running XValidation two times within the SAME process causes different results.

See this setup here (simply copy and paste in the xml-tab)

Code:

<operator name="Root" class="Process" expanded="yes"> <description text="#ylt#p#ygt#This experiment is very similar to the experiment #yquot#03_XValidation_Numerical.xml#yquot#. The basic experiment setup is exactly the same, i.e. the first inner operator must produce a model from the given training data set and the second inner operator must be able to handle this model and the test data and must provide a PerformanceVector. #ylt#/p#ygt# In contrast to the previous experiment we now use a classification learner (J48) which is evaluated by several nominal performance criteria.#ylt#/p#ygt# #ylt#p#ygt# The cross validation building block is very common for many (more complex) RapidMiner experiments. However, there are several more validation schemes available in RapidMiner which will be dicussed in the next sample experiments. #ylt#/p#ygt#"/> <operator name="ExampleSource" class="ExampleSource"> <parameter key="attributes"value="..\data\labor-negotiations.aml"/> </operator> <operator name="MissingValueReplenishment" class="MissingValueReplenishment"> <list key="columns"> </list> </operator> <operator name="IteratingOperatorChain" class="IteratingOperatorChain" expanded="yes"> <parameter key="iterations"value="2"/> <operator name="XValidation" class="XValidation" expanded="yes"> <parameter key="keep_example_set"value="true"/> <parameter key="number_of_validations"value="5"/> <operator name="NearestNeighbors" class="NearestNeighbors"> </operator> <operator name="OperatorChain" class="OperatorChain" expanded="yes"> <operator name="ModelApplier" class="ModelApplier"> <list key="application_parameters"> </list> </operator> <operator name="ClassificationPerformance" class="ClassificationPerformance"> <list key="class_weights"> </list> <parameter key="classification_error"value="true"/> </operator> </operator> </operator> </operator> <operator name="IOConsumer" class="IOConsumer"> <parameter key="io_object"value="ExampleSet"/> </operator></operator>